Space Shuttle to Make Second Launch Attempt Tonight

A nearly full Moon sets as the space shuttle Discovery sits atop Launch pad 39A at the Kennedy Space Center in Cape Canaveral, Florida, in the early morning hours of Wednesday, March 11, 2009.Credit: NASA/Bill Ingalls

CAPE CANAVERAL, Fla. - The space shuttle Discovery is primed for a
second launch attempt tonight after engineers repaired a gas leak that kept the
spacecraft from lifting off last week.

Discovery and her
seven-astronaut crew are poised to blast off at 7:43 p.m. EDT (2343 GMT)
from Launch Pad 39A here at NASA's Kennedy Space Center.

The weather outlook for this evening is promising, with a roughly 80
percent chance of favorable conditions for launch, shuttle weather officer
Kathy Winters said.

Since last Wednesday's foiled
launch attempt, ground crews have completely replaced a suspect connector
between the shuttle's external fuel tank and a vent line that carries flammable
hydrogen gas away from the launch pad. Technicians discovered a leak in the
line after Discovery's tank began fueling last week, prompting mission managers
to call off the launch.

Crews have since worked around the clock to replace the connector seal
and investigate the problem. Though no smoking-gun explanation has yet been
found, mission managers are hopeful that swapping out the offending part will stop
off the leak. If the leak persists today, NASA will call off the launch
attempt, mission managers said.

Discovery is slated for a 13-day
mission to space, featuring three spacewalks to deliver and install the
last section of the International Space Station (ISS)'s backbone-like main
truss. The final segment, called Starboard-6, comes with a complement of new
solar panel wings that should boost the station's power generation capability
by 25 percent.

The shuttle is also set to carry up Japan Aerospace Exploration Agency
astronaut Koichi Wakata to replace NASA astronaut Sandra Magnus as a space
station Expedition 18 flight engineer. Wakata will become Japan's first
long-duration astronaut when he stays aboard the orbiting laboratory until
later this summer.

"These crewmates have been absolutely tremendous to work
with," Archambault said of his team in a preflight NASA interview. "I
look at this crew and I say, 'Boy, you really stacked the deck in my favor and
I?m very appreciative for each one of these guys.'"

If the shuttle launches today, the astronauts' original 14-day mission
will be cut short by one day and one spacewalk, to make room for an incoming
Russian Soyuz mission to the space station launching March 26. If the shuttle
is unable to launch today, NASA can try again Monday and Tuesday, though
launching then will necessitate shortening the mission even further.

Today's launch attempt comes more than a month after Discovery's initial
Feb. 12 launch target. NASA delayed the shuttle's launch for weeks due to
suspect fuel control valves in the orbiter's main engines. The shuttle?s three
valves were each replaced twice, with mission managers clearing Discovery for
launch earlier this month.

NASA?s STS-119 mission will mark the 125th shuttle launch and the 27th mission
for the Discovery spacecraft. The spaceflight is the first of at least five
NASA shuttle missions planned for 2009 to continue space station construction
and perform one last overhaul
of the Hubble Space Telescope.